This study seeks to evaluate, by the use of an infant primate model, the hypothesis that victims of sudden infant death syndrome, (SIDS), might be characterized by predisposing physiologic states, particularly chronic hypoxemia resulting from deficient ventilatory performance. Chronic hypoxemic states will be induced in infant monkeys by production of diffuse ischemic lesions of the brainstem to interfere with ventilatory regulation. Using respiratory function measures and blood-gas analysis, the infants will be compared wwth a control population with respect to adequacy of respiratory control, response to acute change in respipatory gas composition and characterisitics of laryngeal reflexes. Tissues of these animals will be prepared for microscopy and examined quantitatively for indices of chronic hypoxemia, including brainstem astroglyosis, lung arteriole changes, hepatic hematopoiesis, brown fat retention and increased adrenal chromaffin tissue.